The Delta of the 1800's consisted of the tidal islands landscape of the central Delta (blue), the flood basins landscape of the north Delta (green), and the distributary rivers landscape of the south Delta (orange).

A new study released this week by the San Francisco Estuary Institute and the California Department of Fish and Game aims to turn back the clock and learn how the Sacramento-San Joaquin Delta used to work - over 150 years ago.

It's part of an effort to allow scientists to better understand how to restore the Delta, by examining how the massive freshwater estuary functioned, before the gold rush and agriculture transformed the region with levees, shipping channels and dredging.

"There was a general recognition that we didn't really know how it used to work, and that would probably help us understand what native species really need and how we would go about reestablishing some of these features in the future," says Robin Grossinger, a senior scientist with the San Francisco Estuary Institute, who helped author the study.

The task of analyzing the Delta of 160 years ago wasn't easy. After all there weren't satellite photos or GPS maps from the era to look back at. Instead Grossinger says the team relied on a mix of old maps and drawings, vintage photographs, oral histories, and journals such as this one.

"I think maybe our biggest surprise and find was the extensive description and travel account of a guy who got lost in the marshes hunting ducks. And these guys had to spend the night and were hiking through the Delta in the dark, trying to carry lots of ducks, and describing in detail everything they encountered, how deep the ponds they had to wade through were."

The researchers took all of the information and put it into a computer program known as GIS, (geographic information system), and slowly a picture of the old Delta ecosystem began to emerge.

"We were surprised ourselves to see how diverse and complex the landscape was. And then equally it's also impressive once you have that picture to see a lot of pieces that are still left in some shape or form."

Grossinger says that three distinct patterns emerged in their study of the region. In the north part of the Delta along the Sacramento River, you would have once found broad, dense forests as much as half a mile wide. In the central Delta, hundreds of miles of tidal channels used to flow through broad islands of tidal marshes, lakes, and willow fern swamps. The southern part of the Delta was a home to a more open landscape with grassy areas, floodplains and wetlands.

Grossinger says that the effort will help guide future investments and research as the state works to improve the health of the Delta.

"It's not that we're going to reestablish the historical Delta, and we wouldn't want to, even if it was possible, because there's so many things going on there today. But as we're going to make strategic investments to improve the health of the ecosystem, it really does help to understand what native species need and how those kinds of habitat were created by natural processes."

And while only 3 percent of the tidal wetlands that existed in the early 1800's exist in the Delta today, Grossinger remains optimistic that with this new understanding of how the Delta used to work, that future improvements are possible.

"These systems are not going to come back in their full scale ever. But that said, when you see how much has been lost, doing strategic, relatively small but well connected and well designed projects could make a big difference."